Are Whole Grains a Brain Food?

Based on cross-sectional studies of thousands of men and women over the age 50, high whole grain intake is positively associated with the Successful Aging Index, a measure representing not only the avoidance of disease and disability but the maintenance of cognitive function and engagement in physical, social, and productive activities. This was after attempts to control for various other dietary and lifestyle factors, but it’s impossible to control for everything. Randomize mice to barley instead of white rice, and they live significantly longer and even have less hair loss and a glossier coat. In contrast, the human interventional evidence to date is underwhelming.

Over three consecutive days, evening meals of prebiotic-rich whole grain rye bread improved mood compared to those instead randomized to white bread, but failed to affect cognitive test scores. Longer term, a randomized controlled trial that swapped mostly white rice with mostly brown rice for nine weeks in Korean high school students claimed to have found it to be “beneficial for cognitive performance;” yet, the purported effect on mental fatigue appeared to be less brown rice helping than white rice hurting. Yet frankly, with so many different variables tested—more than three dozen!—the few statistically significant differences may very well have just been statistical flukes.

There are two randomized controlled trials of white versus brown rice in elderly individuals. One randomized older men and women to a cup of cooked brown versus white rice for two years, which is impressively long for interventional diet trials. The researchers concluded brown rice may offer “protective benefits against age-related cognitive decline,” but only one of five cognitive measures tested, only a subscore of a single test, showed any real improvement, raising a similar concern about failing to account for statistical flukes arising from multiple comparisons.

The other trial involved nursing home residents in Japan randomized to brown rice three times a day or white for six months, and then the two groups were switched for another six months. The researchers claim the brown rice “contributed to the prevention and reduction of overall cognitive decline;” however, overall, no significant effect was apparent. Their overly rosy assessment appears to be based on a post hoc analysis showing a benefit for a small subgroup who started out with impaired cognition. Those are the ones who need it the most, but we’d need to see these data replicated to have faith in the results.